<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="css/style1.css" class="">
</head>
<body>
    <h1>响应式</h1>
<div class="container">
    <div class="col">1</div>
    <div class="col">2</div>
    <div class="col">3</div>
 </div>

</body>
</html>